Method of producing &#34;duo-sol&#34; raffinate having improved color



A ril 3, 1962 R. A. BEHN 3,028,315

METHOD OF PRODUCING "DUO-SOL" RAFFINATE HAVING IMPROVED COLOR Filed Aug. 13, 1957 \n E o k N) 1 5 y r0 :0

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WLSV H0103 INVENTOR. Robert A. Behn AGENT.

United States atent Ofice 3,028,315 Patented Apr. 3, 1962 3,028,315 METHOD OF PRODUCING DUO-SOL RAFFINATE HAVING IMPROVED COLOR Robert A. Behn, Beaumont, Tex., assignor, by mesne assignments, to Socony Mobil Oil Company, Inc., New

York, N.Y., a corporation of Texas Filed Aug. 13, 1957, Ser. No. 677,895 3 Claims. (Cl. 196-145) The present invention relates to Duo-Sol refining of residual lube oil fractions of mineral oil and, more particularly, to a method of refining residual lube oil fractions of mineral oil by the double solvent technique to produce rafiinates having lighter color.

One of the factors in the cost of producing lubricating oils from residual is the cost of percolation of the dewaxed raffinate to produce a lubricating oil having the color required by the specification. At normal yields, i.e., barrels of rafiinate treated per ton of percolation medium before regeneration, raffinates from residual fractions of mineral oil use 45 percent of the total filter absorbent requirements but represent only 20 percent of the lubrieating oil production. Thus, it is manifest that the cost of percolation of rafinates from residual oils is out of proportion to the volume of oil treated. It has now been found that ratfinate quality can be improved by treating residual oil lubricating fractions at higher temperatures. However, treatment at higher temperatures reduces the yield of rafiinate. On the other hand, higher treating temperatures permit greater throughput of the charge stock providing equivalent production of rafiinate of improved quality. As concomitants of the use of higher treating temperatures it is necessary to increase the phenol content of the cresylic acid solvent, to raise the extraction pressure, and to insulate the extractors to reduce thermal convection currents in the settlers.

The Duo-Sol technique for treating residual oils to recover lubricating fractions meeting specification requirements involves the use of a first solvent having greater solvent capacity for the more paratfinic constituents of the charge stock and a second solvent which has greater solvent capacity for the more aromatic constituents of the charge stock. The two solvents are mutually substantially immiscible. The Duo-Sol technique involves introducing one solvent into the last cell of a plurality of extraction cells, introducing the other solvent into the first cell of a plurality of extraction cells, introducing the charge stock into an extraction cell between the median cell of the plurality of extraction cells and the cell into which the parafiinic solvent is introduced, and flowing the two solvents in countercurrent manner through the plurality of extraction cells. Illustrative of two mutually substantially immiscible solvents are propane as the solvent having greater capability for extracting the more parafiinic constituents of the charge stock and cresylic acid, a mixture of cresols, methyl phenols, and phenol for extracting the more aromatic constituents of the charge stock. In a unit having nine cells the solvent having greater capabilities for extracting the more parafiinic constituents of the charge stock, e.g., propane, is introduced into the first cell. The solvent having greater capabilities for extracting the more aromatic constituents of the charge stock, e.g., cresylic acid is introduced into the ninth cell. The charge stock is introduced into the third cell, i.e., between the median cell, i.e., the fifth cell and the cell into which the solvent for the more paraflinic constituents of the charge stock is introduced, i.e., the first cell. The cell into which the charge stock is introduced is called the feed compartment. The cresylic acid and extracted more aromatic constituents, designated extract, are removed from the first cell. The propane and more parafiinic constituents are designated as the rafiinate and are removed from the last, i.e., ninth cell. The solvent is recovered from the raflinate. The solvent-free rafiinate is dewaxed in any suitable manner as by treatment with methyl ethyl ketone and toluene and filtered. The dewued raffinate is then percolated through clay or bauxite or the like to reduce the color of the raflinate to that required by the specification. The percolated oil is then ready for the addition of one or more additives and subsequent sale. The extract is treated to remove the solvent usually by distillation. The recovered solvents are returned to the extraction unit.

The data presented in Table I were obtained when treating the residuum obtained from a mixture comprising 25 percent by volume West Texas Bright, 45 percent by volume Panhandle-Fullerton and 30 percent by volume East Texas. The West Texas Bright stock is the 3.5 percent on the charge of a West Texas crude. The Panhandle-Fullerton residuum is a 13.5 percent on the charge of a Panhandle-Fullerton crude. The East Texas residuum is the 14.5 percent on an East Texas crude.

1 Selecto a mixture of volume percent phenol, balance-cresylic acids (CH3OaH4OH) I V.I.=viscoslty index.

It will be observed that a raffinate ASTM color of approximately 6 is required to meet a specification color of ASTM 7 after dewaxing. Consequently, a raflinate color of ASTM 5 is lower than necessary to meet'the specification ASTM color of 7. Accordingly, the charge rate can be increased. Thus, although the yield on a percentage basis is lowered by raising the temperature of the feed compartment from 136 F. to F., nevertheless the throughput can be increased to compensate for the lower yield and thus maintain the total production at the level at which a raffinate having an ASTM color of 7 is produced. Since the percolation yield is increased when percolating a dewaxed rafiinate having an ASTM color of 6-(light 6) a commercially important advantage results.

The curves in the figure are illustrative of similar results when treating other residua. Thus, for example, curve 1 represents the relation between the temperature of the feed compartment and the color (ASTM) for the charge stock data for which are presented in Table I. Curve 2 represents the relation between the temperature of the feed cell and color (ASTM) for a residuum obtained from a mixture comprising 33 percent by volume Panhandle and 67 percent by volume Fullerton. The Panhandle residuum is the 18.5 percent on the charge of a Panhandle crude. The Fullerton residuum is the 16.5 percent on the charge of a Fullerton crude. Curve 3 represents the same relation for a residuum from a Grade A Coastal crude. The Coastal residuum is the 12 percent on the charge of a Grade A Coastal crude.

The effect of pressure during extraction is clearly illustrated by the data presented in Table II.

. the charge.

Table II Charge Stock West Texas Bright; East Texas;

% PanhandleFullerton Feed Pot Temp., F 135 140 146 140 140 140 Extraction Pressure,

p.s.i.g 300 300 300 320 335 350 Ratfinate Yield, Vol.

Percent .o 57. 5 54. 5 51 51 51 51 Propane, Wt. Percent on Charge 400 400 400 400 400 400 Selecto Wt. Percent on Charge 225 225 225 225 225 225 Ratfinate Properties SUV at 210 F 147 140 134 137 136 136 Color-Tag 1V; 2% 3% 1% 2% 2% C010rNPA Lt. 8 Dark 6 5 Lt. 7 Lt. 6 Lt. 6 V.I. at 20 F.,

Pour Point".-. 95 96 95 90 1 Feleet0-80% phenol, balance cresols.

9 Color N PA equivalent to Color ASTM.

Lt.-light.

It will be observed that at the same feed cell temperature of 140 F. increasing the extraction pressure from less than 300 p.s.i.g. to 320 p.s.i.g. changed the color of the rafiinate from a dark 6 to a light 6. The percolation yield when the raffinate has an ASTM color of dark 6 is 70 barrels per ton of filtering medium (bauxite for example) before regeneration whereas when the rafiinate has an ASTM color of light 6 the percolation yield, is barrels per ton of filtering medium.

While it is conventional practice to operate uninsulated Duo-Sol units at feed compartment temperature of F., it was found that the convection currents produced in the settling sections of the extraction cells at temperatures of the order of F. and higher hindered the separation of the phases, i.e., propane phase from Selecto phase. Insulation of the compartments of the unit assisted in a more consistent temperature control.

Accordingly, the present invention provides a method in which residual lubricating oil fractions are treated at a feed compartment temperature of at least 140 F., and an extraction pressure of at least 320 p.s.i.g., preferably employing a mixture of phenol and cresols containing at least about 70 percent by volume of phenol and the balance cresols. Solvent dosages employed are about 200 to about 600 percent by weight, preferably about 350 to about 500 percent by weight of propane based upon the charge and about 100 to about 400, preferably about to about 300 percent byweight of Selecto containing at least 70 percent by volume of phenol based upon Preferably, all of the cells or compartments are insulated to maintain the operating temperature sub- 4 stantially constant with a difference in temperature in any cell not more than 10 F. and with a difference between cells or compartments of not more than *25 F.

I claim:

1. In the method of improving the color of Duo-Sol rafiinate wherein a lubricating fraction is extracted in a plurality of stages contemporaneously with a solvent for more parafiinic hydrocarbons comprising propane and a solvent for more aromatic hydrocarbons consisting essentially of at least 70% phenol and the balance, to make 100%, cresols, said solvents being substantially immiscible, and wherein an extraction temperature of at least 140 F. is employed, the improvement which comprises maintaining an extraction temperature which does not vary by more than about 110 F. in any stage.

2. In the method of improving the color of Duo-Sol raffinates which comprises extracting a residuum with about 200 to about 600% by weight of propane, and about 100 to about 400% by weight of a mixture comprising at least about 70% by volume phenol and the balance cresols, in a plurality of stages, at an extraction temperature of at least 140 F. and an extraction pressure of at least about 320 p.s.i.g., the improvement which comprises maintaining in any stage a selected extraction temperature within the range of *-10 F.

3. In the method of improving the color of Duo;01 V

raffinate which comprises extracting in a -plurality of stages a lubricating oil fraction contemporaneously with a solvent for more parafiinic hydrocarbons comprising propane and a solvent for more aromatic hydrocarbons consisting essentially of at least 70% phenol and the balance, to make 100%, cresols, said solvents being substantially immiscible, at an extraction temperature of at least 140 F. and at an extraction pressure of at least 320 p.s.i.g the improvement which comprises maintaining a selected temperature in any stage within the range of :10 F.

References Cited in the file of this patent UNITED STATES PATENTS Furby Aug. 17, 1948 Myers Jan. 15, 1952 OTHER REFERENCES UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 3,028,315 April 3, 1962 Robert A. Behn It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 16 for "residual" read residua Signed and sealed this 4th day of September 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID L- LADD Attesting Officer Commissioner of Patents 

1. IN THE METHOD OF IMPROVING THE COLOR OF "DUO-SOL" RAFFINATE WHEREIN A LUBRICATING FRACTION IS EXTRACTED IN A PLURALITY OF STAGES CONTEMPORANEOUSLY WITH A SOLVENT FOR MORE PARAFFINIC HYDROCARBONS COMPRISING PROPANE AND A SOLVENT FOR MORE AROMATIC HYDROCARBON CONSISTING ESSENTIALLY OF AT LEAST 70% PHENOL AND THE BALANCE, TO MAKE 100%, CRESOLS, SAID SOLVENTS BEING SUBSTANTIALLY IMMIS- 